The invention relates to an adhesive tape for flying splice (flying reel change) and to a splice method using such an adhesive tape, especially in paper-converting machines, printing machines and the like.
Flying splice in papermills, film-producing plants or the like is a common technique for replacing an old, almost fully unwound roll of paper by a new roll without having to stop the machines, with run at high speed. This is done using double-sided self-adhesive tapes, so-called tabs, which possess high adhesion and high tack. These tabs are bonded artistically in a zigzag form to the beginning of the web, a procedure requiring experienced personnel, with only about 4-5 minutes"" time remaining for the entire procedure, owing to the high speed of the machines.
Although this technology is well established, it is not without certain disadvantages. Thus, experienced personnel are required, the procedure is intrinsically hectic, and the bonds are also relatively thick, since in each case two plies of web and the adhesive tab in between are the result: a result which is unwanted in the industry.
There are various products on the market, known as splicing tapes, for this xe2x80x9cbutt splicingxe2x80x9d in flying splice, which are coated on both sides with pressure-sensitive adhesive composition. Adhesive tapes of this kind are marketed, inter alia, under the name tesafix (Beiersdorf).
The prior art describes diverse adhesive tapes for such purposes. For instance, EP 418 527 A2 discloses a method of preparing a reel of printing material in web form for automatic reel changers and an adhesive strip suitable for this purpose. DE 40 33 900 A1 also describes an adhesive tape suitable for a splice point. A disadvantage, however, are adhesive regions which lie exposed after the splice method has been implemented.
The nonadhesive masking of otherwise exposed adhesive areas is taught by U.S. Pat. No. 5,702,555 for more static loadings while securing a reel start, while DE 196 32 689 A2 discloses an adhesive tape of this kind for dynamic loading during the splicing method, the paper backing of this tape cleaving and masking the adhesive compositions with its residues.
Also of this kind is an adhesive tape in accordance with DE 196 28 317 A1, likewise for a splicing method. This adhesive tape carries, on its nonadhesive reverse, a double-sided adhesive tape (6) which has a paper backing (7) which is suitable for splicing and which cleaves (7a, 7b, FIG. 3) during the splicing method and masks the respective adhesives. This double-sided adhesive tape (6) ends at the side with one side of the paper backing (2); it is, therefore, arranged along one of the long edges of the adhesive tape.
In practice, even these adhesive tapes exhibit disadvantages, primarily because a splice does not succeed but instead ends as a break, without any evident reason for this.
In particular, it was necessary to solve the problem of developing an adhesive tape with which carrier materials in web form which are under tension may be joined reliably to one another.
It is an object of the invention to provide a remedy here.
This object is achieved by means of an adhesive tape and splicing method as detailed in the claims. In order to avoid repetition, reference is made expressly to the claims, especially with regard to preferred embodiments.
In accordance with the invention, splices succeed without breaks, a preferred feature being the offset or distance V of the double-sided adhesive tape DO from the long edge LK of the adhesive tape.
In accordance with the invention, there are relevant advantages for practical use:
Tensile strength and elongation at break characteristics are much more readily controllable with film systems than in the case of paper backings. As a result it is possible to splice even those carrier systems which are highly sensitive to tearing. The products may be adapted steplessly to the carrier systems that are to be spliced.
Film systems exhibit no dimensional changes as a result of climatic conditions, and so the bales prepared for splicing can be stored for longer. Bale product spliced using paper systems must be supplied to the splicing operation immediately after preparation (dependent, of course, on the ambient climatic conditions).
Film systems are better suited to mechanical processing (i.e., automatic attachment of the splice) owing to increased tensile strength and improved flatness.
Coextruded polymeric composite systems may be produced in a defined manner in one operation, inexpensively and with few fluctuation parameters.
Cleaving Systems
The cleavable system advantageously has a markedly lower cleavage resistance than the principal carrier (P1) which has to accommodate the tensile forces. A sufficient difference is helpful for the functional principle of the product of the invention.
Suitable cleaving systems include, for example, the following papers or paper composite systems or polymeric composite systems:
Duplex papers: These papers are standard commercial products and are used, for example, in the production of filter materials and wallcoverings.
Readily cleaving papers: The cleavage work is adjusted by way of the consolidation of the paper fiber structure. The lower the consolidation, the lower the cleavage work.
Suitable paper types include, for example, machine-finished papers calendered on one side or else highly calendered kraft papers.
Sized paper systems or sized film systems: The cleavage work is adjusted by way of the chemistry of the pressure-sensitive adhesive or of the coating system. The sizing or pressure-sensitive adhesive should have penetrated into the paper only to an insignificant extent.
Coextruded polymeric composite systems: Extruded multilayer systems with low bond strength between the boundary layers.
Polymer nonwovens: The cleavage work is adjusted by way of the chemistry of the fixatives.
Clean cut edges are also helpful for the objectives of the present invention. During the cutting operation, no composition should be squeezed out. In particular, the cleavable attachment area of the cleaving material should not be covered by a pressure-sensitive adhesive composition.
The amount by which the cleavable material is set back, or the distance V, should in accordance with the invention be 0-15 mm, especially 0.5-15 mm, especially 1-7 mm, and very particularly 1.5 mm-3.5 mm.
Suitable cleaving paper comprises a variety of cleavable paper systems, such as
Duplex papers (papers laminated together in a defined manner); the process of cleavage proceeds extremely homogeneously, no stress peaks are produced as a result, for example, of inhomogeneous consolidation. These papers are used for the production of wallcoverings and filters.
Readily cleavable paper systems
Highly consolidated papers sized together in a defined way (xe2x86x92 paper with a high cleavage strength). Sizing may be carried out, for example, using starch, starch-containing derivatives, wallpaper adhesives based on methyl cellulose (Methylan(copyright), Henkel KGaA, Dusseldorf, Germany) or else based on polyvinyl alcohol derivatives.
The width of the cleaving system is preferably 3-35 mm, especially 6-12 mm.
Suitable self-adhesive compositions include all typical pressure-sensitive adhesive compositions, especially
Acrylates (water-soluble and water-insoluble)
Natural rubber compositions, synthetic rubber compositions
The splicing method, in this case the bonding operation using the splicing tape, may in particular take place in such a way that the adhesive tape is bonded to the running web at right angles (disadvantage: the cleavable system must cleave completely within fractions of seconds) but also at an acute angle (advantage: the process of cleavage runs as a wave through the adhesive tape), in particular up to 45xc2x0, especially up to 15xc2x0.